From 1eecd73cce4e11ba9d67ad767f92069cfba7b589 Mon Sep 17 00:00:00 2001 From: Andi Kleen <ak@suse.de> Date: Fri, 19 Aug 2005 06:56:40 +0200 Subject: [PATCH] [PATCH] x86_64: Fix race in TSC synchronization Plug a race in TSC synchronization We need to do tsc_sync_wait() before the CPU is set online to prevent multiple CPUs from doing it in parallel - which won't work because TSC sync has global unprotected state. Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org> --- arch/x86_64/kernel/smpboot.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) diff --git a/arch/x86_64/kernel/smpboot.c b/arch/x86_64/kernel/smpboot.c index b15761ff41010..fa25e39fe54df 100644 --- a/arch/x86_64/kernel/smpboot.c +++ b/arch/x86_64/kernel/smpboot.c @@ -492,6 +492,14 @@ void __cpuinit start_secondary(void) */ set_cpu_sibling_map(smp_processor_id()); + /* + * Wait for TSC sync to not schedule things before. + * We still process interrupts, which could see an inconsistent + * time in that window unfortunately. + * Do this here because TSC sync has global unprotected state. + */ + tsc_sync_wait(); + /* * We need to hold call_lock, so there is no inconsistency * between the time smp_call_function() determines number of @@ -509,13 +517,6 @@ void __cpuinit start_secondary(void) per_cpu(cpu_state, smp_processor_id()) = CPU_ONLINE; unlock_ipi_call_lock(); - mb(); - - /* Wait for TSC sync to not schedule things before. - We still process interrupts, which could see an inconsistent - time in that window unfortunately. */ - tsc_sync_wait(); - cpu_idle(); } -- 2.30.2